Two electrode arrangement for electric glow discharge chamber



y 1961 B. BERGHAUS ET AL 2,994,007

Two ELECTRODE ARRANGEMENT FOR ELECTRIC GLOW DISCHARGE CHAMBER Filed Jan. 25, 1960 INVENTORS 6L1 BY F A'H'ornev United States PatentOfi ce I Patented July 25, 19st This application is a continuation-in-part of the e pending application Serial No. 410,932, filed February 17, 1954, now abandoned, and relates to two electrode arrangements for electric glow discharge chambers and particularly to lead-in devices using such an arrangement.

Lead-in devices for electric conductors in glow discharge vessels protected against the destructive effect of the discharge with screening means having intermediate gaps provided in front of the insulating material cause technical and operation difliculties if during the operation at high pressures the thickness of the glow seam is so reduced that the intermediate gaps between the walls forming them have to be made of very small dimensions if they are intended to prevent the occurrence of discharges of large energies. The dimensions of these dis tances are within the region of the lower minimum limits of the tolerances which can be produced with the present technical means, even in the case of rotary bodies, and even when the most modern machining processes, such as grinding, lapping, etc., are used, whereby it has also to be taken into consideration that we are partly concerned with ceramic bodies, such as insulators or the like in which these processes encounter difliculties. It has been found in practice that in the case of such small distances one is not in a position to produce them quite uniformly, so that places occur where the gap has different widths, whereby the danger of a flash-over arises which interrupts the operation.

One embodiment of the invention is a lead-in for a glow discharge vessel having two concentric electrodes enclosing a gap which, seen from the interior of the vessel, is disposed in front of an insulator that lies between the electrodes, and the invention consists in that one electrode, or parts thereof, is arranged with respect to the other electrode so that it is movable and can be adjusted in position. consists of a ring, which is secured to it by an easily de tachable connection allowing of a radial displacement, for instance, by screws passing through larger holes in the ring. It is especially advantageous if one part of the movable electrode consists of a ring which is secured to it by an easily detachable connection allowing of a radial and axial displacement. The same advantages are obtained in the case of a gas discharge operated with alternating currents. A characteristic feature of the device according to the invention is the capability of displacement of an electrode part which is easily accessible in the constructional arrangement of the gap system.

The accompanying drawing illustrates by way of example, a construction of vacuum vessel according to the invention, as used for the treatment of work-pieces or for the carrying out of chemical reaction by means of gas discharges of high intensity.

The glow discharge chamber or vessel is provided with a double-wall bottom 1, 2 forming a cooling space 3 through which passes a cooling means, the'space above the wall 1 representing the interior of such chamber or vessel. If the vessel wall 11, 2 is connected as an anode, the cathode 4, provided with a screw-threaded attachment 5, is led through the outer insulator '6 in order to secure the parts to be treated. Cooling of the cathode is effected through its whole length by the cooling means Further, a part of the movable electrode 2 entering at '7 and leaving at 8. A screw-cap 9 presses the insulator 6 against a packing 10, which is provided in the screw-threaded connector 11 of the bottom of the vessel. Rubber synthetic resins or the like are preferably used as packing material. The position of the anode cap 13 at the interior of the discharge space is fixed by the anode ring 14. The latter forms an annular cylindrical gap 16 with respect to the cathode ring 26, which gap of of the greatest importance for the operation of the lead-in. The electrode 4 is separated from the wall '1, 2, connected as a counter-electrode, e.g. as the anode, by the insulator 15, part of which is spaced from such wall to provide a gap 17, acting as a further screening gap for insulator 15, the gap 17 communicating with the gap .16. It will be understood that the principal glow discharge occurs between the work-pieces mounted on the attachment 5 and the chamber wall, and that the gaps 16 and -17 act to hinder the glow discharge from reaching the insulator 15, p I

In order to represent the essence of the invention more clearly, the internal insulator 15 is shown exaggerated as I to its accuracy by this that the wall surface 15 shown in the right hand side deviates by the inaccurate value 18 from the stereornetrically exact cylindrical boundary 15". For this reason, the gap 17" on the right hand side of the drawing appears smaller than the gap 17 on theleft hand side, and likewise the gap 16. Owing to the reduction in the annular cylindrical gap 17, the reliable operation of the lead-in is not thereby substantially affected. On the other hand, a non-uniform wall distance of the parts 14 and 26 in the region of the gap part 16 would be'a disadvantage, since this part of the gap lies between metal parts of opposite potential, andthe possibility of a release of a flash-over is increased by the widening and the narrowing exceeding a definite value. The gap part 16 between the electrode rings 14 and 26 is protected against the effects of a flash-over by the radially extending gap part 20, which is provided in front of gap 16 and communicated therewith and which is formed by an extension 19 of the anode cap 13 overhanging ring 14 and therefrom. The dimensioning of the protecting gap 16 must be as uniform as possible and is of paramount importance.

For this purpose, the following measures are provided in the example illustrated.

The wall 1 facing the discharge space 12 is provided a at 21 with a recess, which is intended to receive the displaceable plate 22. The latter determines the seat of the anode ring 14 and therewith the shape of the gap 16. In order to enable displacement of plate 22 to be effected, the diameter of the recess 21 is made greater than the outer diameter of the plate 22. The latter is provided at 23 with a number of holes, the diameter of which is again greater than the diameter of the stem 24 of the fixing screws 25, the screw-threaded part of which engages in corresponding screw-threaded bores in the part 1. It is accordingly only necessary to loosen the screws 25 to effect a displacement of the plate 22. If the screws 25 are tightened, the plate 22 is also fixed in position and therewith also the anode ring 14. In this way, the gap 16 can be adjusted very accurately to the same distance between the parts 14 and 26.

As in the course of operation, wear of the structural parts forming the gap will occur, for instance due to dusting, occasional grinding to eliminate rough spots, etc., it is of great advantage to provide also for an axial adjustment of such parts, in order to be able to achieve an exact alignment also in die axial direction. In the example illustrated, the gap 20 must be readjusted by adjustment of the distance between ring 26 and cap 13, in order that it may not exceed a specific width, as otherwise it could no longer fulfill satisfactorily its function of protection against the glow discharge. For this purpose, for instance, ring 14 does not merely rest on adjustment plate 22, but is connected thereto in such manner that such ring, and with it the cap 13, may be raised and lowered, thereby adjusting the axial distances between parts 13 and 26.

It will be understood that the invention is not limited to the above described lead-in devices, but the scope of the invention includes other two electrode arrangements for electric glow discharge chambers comprising two electrodes arranged one Within the other and spaced from each other, at least one of the electrodes being adapted for connection to an electric potential, one of the electrodes being adjustable in at least one of the axial and radial directions with respect to the other electrode. Said electrodes, by example a metallic tube as outer electrode and a metallic rod as inner electrode within the outer electrode, forming a gap between them which is open to the interior of the chamber or vessel. According to the invention, the said adjustable electrode being movable to make the width of the gap the same throughout its whole extent.

A two electrode arrangement of that kind is per example a rifle barrel being fastened direct to the lead-ins one electrode and having a rod as inner electrode extending throughout the bore of the rifle barrel and forming a gap with the interior of the bore. It is important in such two electrode arrangements that the rod is adjustable at least in the radial direction with respect to the tube to make the width of the gap the same throughout the whole extent of the bore.

What we claim is:

1. A current lead-in device for electric glow discharge chambers comprising two electrodes arranged one within the other and spaced from each other, at least one of the electrodes being adapted for connection to a source of electric potential, an insulator between the electrodes,

one of the electrodes being adjustable in at least one of the axial and radial directions with respect to the other electrode, said electrodes forming a gap between them which is disposed in advance of the insulator viewed from the interior of the chamber, said adjustable electrode being movable to make the width of the gap the same throughout its whole extent.

2. The device as claimed in claim 1, wherein the two electrodes are of circular outline and include parts which are fixed with respect to each other, one of the electrodes including an adjustable part which is movable to bring the electrodes into concentric relation.

3. The device as claimed in claim 1, wherein the adjustable electrode comprises a fixed part and a ring detachably secured to such fixed part to enable the ring to be radially displaced with respect to the other electrode.

4. The device as claimed in claim 3, wherein the detachable connection comprises screws entering tapped bores in the said other electrode and passing through holes in the ring which are of larger dimension than the diameter of the stem of the screws.

5. The device as claimed in claim 1, including adjusting means for said adjustable electrode exposed to the interior of the chamber and thus easily accessible from inside the chamber.

6. A two electrode arrangement for electric glow discharge chambers comprising two electrodes arranged one within the other and spaced from each other, at least one of the electrodes being adapted for connection to an electric potential, one of the electrodes being adjustable in at least one of the axial and radial directions with respect to the other electrode, said electrodes forming a gap between them which is open to the interior of the chamber, said adjustable electrode being movable to make the width of the gap the same throughout its whole extent.

No references cited. 

